Dockets Management Branch (HFA-305) Food and Drug ... BIO...Feb 27, 2013 · drug development preclinical program. We suggest including an introductory paragraph that reads: “The

February 27th, 2013

Dockets Management Branch (HFA-305)

Food and Drug Administration

5630 Fishers Lane, Rm. 1061

Rockville, MD 20852

Re: Docket No. FDA–2012-D-1038: Guidance for Industry: Preclinical

Assessment of Investigational Cellular and Gene Therapy Products.

Dear Sir/Madam:

The Biotechnology Industry Organization (BIO) thanks the Food and Drug Administration

(FDA) for the opportunity to submit comments on the Guidance for Industry: Preclinical

Assessment of Investigational Cellular and Gene Therapy Products.

BIO represents more than 1,100 biotechnology companies, academic institutions, state

biotechnology centers and related organizations across the United States and in more

than 30 other nations. BIO members are involved in the research and development of

innovative healthcare, agricultural, industrial and environmental biotechnology products,

thereby expanding the boundaries of science to benefit humanity by providing better

healthcare, enhanced agriculture, and a cleaner and safer environment.

GENERAL COMMENTS:

BIO believes this document will be very helpful for developers of novel biologics and we

appreciate the efforts of the Center for Biologics Evaluation and Research/Office of

Cellular, Tissue, and Gene Therapies (CBER/OCTGT) in producing this Guidance. In

support of the Draft Guidance, we offer several general comments.

A. Analogy to Drugs

BIO appreciates the analogy to the activity, safety, and kinetics of drug/protein

therapeutics utilized in the Guidance. We believe this is a useful starting point for

explaining the key objectives of all preclinical translational programs.

B. Organization of Guidance Document

Overall, we suggest that it would help the readability and improve the clarity of the

document if this Guidance were made more succinct. A practical way to accomplish this

without losing content is to consolidate comments that apply to all three product types,

and place them in Section III.B.2-3. As a result, each of the specialty product

BIO Comments on Preclinical Assessment of Investigational Cellular and Gene Therapy Products FDA Docket: FDA–2012-D-1038 February 27th, 2013 Page 2 of 29

subsections would then focus on program design aspects that are unique to the

particular product class.

C. Novel Delivery

BIO believes guidance on co-development of novel formulations or devices used for

delivery of cells or gene therapy is necessary, as many investigators are working with

novel delivery methods.

D. Scope

The Draft Guidance document indicates that it will address expectations to support both

Investigational New Drug (IND) and Biological Licensing (BLA) applications. However,

the Draft Guidance focuses primarily on INDs. We believe that consideration should be

given to expanding the discussions in the Draft Guidance to include non-clinical

assessments relevant for a BLA filing (e.g. Developmental and Reproductive Toxicology

(DART) studies). While we expect that treatments for lethal genetic disorders will be

exempt from these tests, the expectations for treatment of milder conditions, such as

connective tissue damage in athletes, or even more severe conditions, such as burn

injury, are unclear.

E. Cell Therapy

Nomenclature – It is especially important to distinguish the risks associated with “stem

cell” therapies (such as embryonic stem cell and induced pluripotent stem cell (iPSC)

therapies) from those of adult tissue-derived and somatic cell therapies (e.g. bone

marrow-derived mesenchymal cells). To better illustrate this distinction, please utilize

the term, “somatic cells” and make reference to prior somatic cell Guidances. This will

help readers to appreciate and define the attributes of their cell-based therapy (CBT).

Sections Section IV, C & D (Overall Study Design and Safety) - Please consider

combining the considerations for “study design” and “potential safety concerns.” Many

of the aspects listed could be removed and considered in the Section III.B.2. as

mentioned above. Of the remainder, many aspects listed apply equally well to both

safety and efficacy studies, since often both aspects are evaluated in the same or similar

models. We have included detailed comments on this topic on pages 19-21 of the chart

below.

CONCLUSION:

BIO appreciates this opportunity to comment on the Guidance for Industry: Preclinical

Assessment of Investigational Cellular and Gene Therapy Products. Specific, detailed

comments are included in the following chart. We would be pleased to provide further

input or clarification of our comments, as needed.


Sincerely,

/S/

Andrew W. Womack, Ph.D.

Director, Science and Regulatory Affairs

Biotechnology Industry Organization (BIO)


SPECIFIC COMMENTS

SECTION ISSUE PROPOSED CHANGE

I. INTRODUCTION

In order to make clear what is defined as a

gene or cell therapy or a therapeutic

vaccine, the scope of products should be

outlined in the introduction.

We recommend that a high level scope similar to what is

present in the introductions of each section IV, V and VI be

added into the introduction. This should be right after the

first footnote. Specific examples of detailed product

divisions can be provided within the individual product

sections in their introductions.

II. BACKGROUND

Page 3; 2nd and 3rd

paragraph:

BIO appreciates that CBER utilizes a

flexible approach to preclinical evaluation

of a candidate therapeutic. However, we

would hope that such an approach would

apply to any pharmaceutical. This also

appears to be a lengthy means by which

to convey this point.

We suggest that the last two paragraphs be consolidated to

one or two sentences regarding open communication with

CBER regarding innovative therapies.

Page 3: “Inherent in such an approach to

regulation is the need for communication

between the sponsor and the review

office.”

We are very encouraged to see that the

Draft Guidance offers early interactions

with FDA with regard to preclinical testing.

However, we do not believe there are any

guidelines for response timelines available

for this early (pre-clinical) stage of

development. Guidance as to FDA

Please provide guidance on FDA response times (30-day,

60-day) for early-stage interactions.



response times (30-day, 60-day) would be

useful. The inclusion of established

timelines will help Sponsors plan

accordingly, and will be useful in

mitigating Sponsor expectations in regard

to FDA responses.

The reference to ICHS6, which should, as

the internationally agreed upon guidance

on biologics development, apply in many

ways to the development of gene and cell

therapies, does not appear until page 8

(footnote 7). It is suggested that this

footnote be moved to this section.

Please move footnote 7 to this section.

III. PRECLINICAL STUDY CONSIDERATIONS

A. PRECLINICAL PROGRAM OBJECTIVES

Page 3; A: “Establishment of biological plausibility” is

not clear.

We suggest simply stating: “Establish proof of concept” and

possibly citing: Au P, et al. (2012) FDA Oversight of Cell

Therapy Clinical Trials. Sci Transl Med 4, 149fs31.

Page 3; A: This entire section is consistent with every

drug development preclinical program.

We suggest including an introductory paragraph that reads:

“The overall objectives for these products are the same as

those for any drug development program. Unique

objectives for cell and gene therapy preclinical programs

will be highlighted in their individual sections.”

B. RECOMMENDATIONS FOR GENERAL PRECLINICAL PROGRAM DESIGNS



Page 4; B.1: “When possible, the investigational CGT

product that will be administered to the

patient population should be used in the

definitive preclinical studies”

Please amend the text to read:

“When possible, the investigational CGT product that will be

administered to the patient population, or a representative

batch, should be used in the definitive preclinical studies.”

Page 4; B.1: “Each lot of an investigational CGT product

used in the preclinical in vitro and in vivo

studies should be characterized according

to prospectively established criteria.”

We recommend clarifying the language to

avoid the possible implication that early

discovery lots be characterized to the

extent that, for instance, safety

assessment toxicology lots are

characterized. Full characterization of

early discovery lots is not feasible since

many analytical methods and criteria are

developed in parallel with later process

development.

Please reword the phrase to the following:

“Each lot of an investigational CGT product used in the

preclinical in vitro and in vivo studies should be

characterized according to prospectively established criteria

meet scientifically appropriate criteria, consistent with the

stage of development.”

Page 4; B.1: Homologous products (surrogates) can be

used when species specific issues arise.


“...testing the product intended for clinical administration in

animals may not be informative, and as such the testing of

a homologous product may be performed if available.”

Page 4; B.2: “The animal species selected for

assessment of bioactivity and safety

should demonstrate a biological response

to the investigational CGT product similar

Please consider defining “biological response” as the

following:

“a pharmacodynamic response that could be measured by



to that expected in humans.”

We recommend further clarifying that

“biological response” could be

demonstrated using a surrogate endpoint

or use of specific biomarkers. Without

additional clarification, the term “biological

response” could be interpreted to limit

species selection to animal models of

disease; and as outlined on Page 5 of the

guidance, there are several technical

limitations in utilizing preclinical animal

models of disease for assessment) in

studies to identify dose and/or toxicity.

surrogate endpoints or biomarkers.”

Page 4; B.2: “Some factors that should be considered

when determining the most relevant

species include…”

“Most” relevant might be an animal

species where testing cannot be done.

The important term is “relevant” so that

extrapolations to human can be done.

Delete the word “most” so the text reads:

“Some factors that should be considered when determining

the most relevant species include…”

Page 4-5; B.2: “3) immune tolerance to a human CT

product or human transgene expressed by

a GT product”

The term immune “tolerance” invokes

several different definitions, depending on

scientific field.

Please clarify what meant is by tolerance (i.e. tolerability or

unresponsiveness).



Page 5; B.3 and Page

11; B.7:

The guidance document includes the value

of conducting studies in a disease/injury

model in understanding benefit/risk

assessments for a cell/gene therapy. The

guidance document also highlights several

limitations associated with the conduct of

such studies. Section 7 indicates that

compliance with Good Laboratory Practices

(GLP) is recommended, but not required.

Given the challenges highlighted with conducting studies in

disease/injury models, clarity regarding FDA’s position on

the critical criteria that should be incorporated into such

studies when GLP compliance is not possible or practical

would be of value to Sponsors.

Page 5; B.2: ““Non-standard” test species, such as

genetically modified rodents (i.e.,

transgenics or knockouts) or large animals

(e.g., sheep, pigs, goats, and horses) may

be acceptable…”

Please delete horse from the list of large animals, as this is

a very infrequently used species.

Page 5; B.2: “...we recommend in vitro studies (e.g.,

functional assays, immunophentotyping,

morphologic evaluation) and in vivo pilot

studies prior to initiation of the definitive

studies...”

We suggest rewriting this statement to read:

“Prior to initiation of the definitive nonclinical studies,

Sponsors should consider using pilot in vitro and/or in vivo

studies to establish the biological relevance of the specific

animal species to the investigational product(s).”

Page 6; B.3: “We recommend that, when appropriate,

Sponsors consider using a tiered approach

for determining selection of an appropriate

animal model…”

The first sentence in this paragraph encouraging Sponsors

to use a tiered approach is a very complete and concise

way to convey the need to employ a rational scientific

approach.

We suggest deleting the text after the first sentence in this

paragraph.



Page 7; B.4: “A primary objective of POC studies is to

establish the feasibility and rationale for

use of an investigational CGT product in

the targeted patient population…”

This paragraph appears too dense for a

simple introduction, and also suggests that

all novel therapies have “substantial

inherent risks”.

We suggest amending the paragraph to read:

“A primary objective of POC studies is to establish the

feasibility and rationale for use of an investigational CGT

product in the targeted patient population. POC studies help

inform the benefit side of the risk-benefit assessment of the

CGT product. Such data may be essential in the assessment

of novel products where these products may have

permanent effects. with substantial inherent risks that have

no previously been assessed in clinical trials In addition,

data from POC studies can contribute significantly to animal

species selection (refer to Section III.B.2. of this

document).

Page 7; B.4: “POC studies should provide data that

demonstrate the following:”

In some cases, POC studies may not be

able to answer some of these questions.

This bullet point list can be consolidated

and made more concise. We recommend

linking back to the plans for human

clinical trials.


“POC studies should provide data that demonstrate the

following: investigate and optimize the route of

administration, method of delivery and administration

schedule as relevant to the human.”

Page 7; B.4: “Data derived from in vitro and in vivo

preclinical POC testing should guide the

design of both the preclinical toxicology

studies...”

This may be contradicting statements

elsewhere in the document where it is

suggested that both POC and Tox

We suggest amending the sentence to read:

“Data derived from in vitro and in vivo preclinical POC/Tox

testing should can guide the design of both the preclinical

toxicology studies, of early-phase clinical trials…”



endpoints can be used in the same study.

This may lead to unnecessary use of

animals when POC and pivotal tox studies

could be the same.

Pages 8-10; B.5: There are two bullet point lists in this

section that outline points by small letter.

Please resolve formatting so that points in section III.B.5.

can be reference without being confused as to which “a” or

“b” is being referred to.

Page 8; B.5b: “The amount and quality of published

preclinical or clinical safety information for

the specific CGT product under

investigation or for a similar product (i.e.,

known toxicities or adverse effects).”

This is an important point that Sponsors

should be aware of in keeping with the 3Rs

initiatives that are outlined in section

III.B.8.

We suggest adding text to make reference to the section

outlining the 3Rs –

“Importantly, such information can help in refining the

study design and reduce animal usage – refer to section

describing 3Rs (III.B.8)”

Page 8; B.5e: “The biological responsiveness of various

animal species to the investigational CGT

product.”

The word “various” may be at odds with

the 3Rs, as it might suggest to some

Sponsors that more than one species is

necessary for toxicology evaluation.


“The biological responsiveness of various animal species to

the investigational CGT product of the toxicology species.”

Page 8; B.5f-h: In the interest of reducing text, bullet

points f-h can be consolidated.

Please combine points f-h to read:

“f. The nature of the product, the MOA and the models



used”

Page 8-9; B.5: “Although healthy animals represent the

standard model test system employed to

conduct traditional toxicological studies,

POC study designs using animal models of

disease/injury are frequently modified to

incorporate important safety parameters

that allow for assessment of the potential

toxicology of an investigational CGT

product”

To clarify, animal models of disease may

be used to obtain safety information in lieu

of studies in healthy animals. We believe

this is a possible route for Sponsors to

investigate, especially if pharmacology is

most notable in an animal model of

disease. This path is also of particular

interest to the gene and cell therapy fields,

as clinical trials are never performed in

healthy volunteers for this class of

therapies.

Please amend the statement to read:

“Although healthy animals represent the standard model

test system employed to conduct traditional toxicology

studies, POC study designs using animal models of

disease/injury are frequently modified to incorporate

important safety parameters that allow for assessment of

the potential toxicology of an investigational CGT product –

such data could possibly be used in lieu of studies in

healthy animals.”

Page 9; B.5a: The text reads: “Adequate numbers of

animals per gender (as applicable) that

are appropriately randomized to each

group. The number of animals required

will vary depending on the novelty and/or

existing safety concerns for the

investigational CGT product, the species,

model, delivery system, and product

It is unclear how group sizes would be affected by the

product novelty or class. We suggest deleting the words

“novelty” and “product class” from this bullet so the text

reads:

“Adequate numbers of animals per gender (as applicable)

that are appropriately randomized to each group. The

number of animals required will vary depending on the



class.”

novelty and/or existing safety concerns for the

investigational CGT product, the species, model, and

delivery system, and product class.”

Page 9; B.5b: “Appropriate control groups. Examples

include animals who do not receive

product...”

It is unclear what “do not receive product”

means. Does this mean untreated? Or

does it mean the following examples

provided? Could this mean sham surgery?

If not, sham surgery should be added.

We suggest adding “are left untreated, who receive sham

surgery (if surgery is employed) so the text reads:

“Appropriate control groups. Examples include animals who

are left untreated, who receive sham surgery (if surgery is

employed), animals administered formulation vehicle only,

adjuvant alone, null vector, delivery device plus formulation

vehicle, or scaffold alone. Justification should be provided

for the specific control group(s) selected.”

Page 9; B.5c: “Multiple dose levels of the investigational

CGT product, which should bracket the

proposed clinical dose range.”

In many cases it may not be possible to

“bracket the clinical dose” due to test

article concentrations.

We suggest adding “use a pharmacologically active dose

and a multiple if possible” so the text reads:

“Multiple dose levels of the investigational CGT product,

which should use a pharmacologically active dose and a

multiple if possible which should bracket the proposed

clinical dose range.”

Page 9; B.5e: The ability to mimic the route of

administration intended for clinical use

may present difficulties for some delivery

systems and result in limited data from

such models or the need to use a Route of

Administration (ROA) that is different from

that intended for the clinic.

Examples of flexibility in addressing the ROA would be

helpful in understanding the general principles of study

designs for delivery to a target site using an alternative

method/device appropriate for the animal species that the

FDA would consider appropriate.

Page 10; B.6: “To assess the potential risks associated

with the method of product administration,

We propose adding the following statement to this



the delivery device system used in the

definitive preclinical studies should be

identical to the planned clinical product

delivery device, if possible.”

The Draft Guidance doesn’t elaborate in

cases where it might not be possible to

use the intended clinical device (e.g.

human device not suitable for animal use).

paragraph:

“In cases where the planned clinical product delivery device

cannot be used for preclinical studies, the Sponsor should

provide justification for any differences.”

Page 11; B.7: “Compliance of in vitro and in vivo

pharmacology/POC studies with GLP is

recommended, but not required.”

Pharmacology studies have never been

required to be conducted under GLP

compliance. Regardless of the statement

that they are “recommended, but not

required”, such text could serve to confuse

Sponsors that they are safer making all

studies GLP-compliant.

We suggest amending the statement to read:

“Compliance of in vitro and in vivo pharmacology/POC

studies with GLP is recommended but not required is not

required. In the event that pivotal safety information is

planned to be obtained from such studies, having portions

of the study performed under GLP compliance (i.e.,

histopathology) is recommended if possible.”

Page 12; B.7: “All preclinical studies that incorporate

safety parameters in the study design

should be conducted using a prospectively

designed study protocol. Results derived

from these studies should be of sufficient

quality and integrity to support the

proposed clinical trial. A summary of all

deviations from the prospectively designed

study protocol and their potential impact

on study integrity and outcome should be

Please consider narrowing the term “All preclinical studies”

to specify “all preclinical toxicology studies,” or consider

providing specific exceptions that take into account

preclinical studies that incorporate safety parameters but

are not required to have a prospectively designed study

protocol.



provided in the preclinical study report.”

The term “All preclinical studies” is overly

broad. There are many instances where a

preclinical study that incorporates safety

parameters should not be required to have

a prospectively designed study protocol.

Most preclinical toxicology studies are

routinely performed in compliance with

GLP, which includes having a prospectively

designed study protocol. However,

preclinical studies that are performed in

early discovery typically do not have a

formal protocol or summary of deviations.

As such, it would be helpful to differentiate

between the expectations for preclinical

studies that are performed in early

discovery with those that are performed

later in development or just prior to the

start of first-in-human studies.

IV. RECOMMENDATIONS FOR INVESTIGATIONAL CELL THERAPY (CT) PRODUCTS

A. INTRODUCTION

Page 14; A: “CT products vary with respect to

characteristics such as formulation

(including combination with a scaffold or

other non-cellular component), ROA, the

genetic relationship of the cells to the

patient (autologous, allogeneic,

Please delete ROA so the text reads:

“CT products vary with respect to characteristics such as

formulation (including combination with a scaffold or other

non-cellular component), ROA, the genetic relationship of

the cells to the patient (autologous, allogeneic,



xenogeneic), and the cell source.”

It is not clear why ROA would be

considered a characteristic of a specific

product because the same CT product may

be used for different routes of

administration.

xenogeneic), and the cell source.”

Page 14; A: “CT products can be generally classified

as: 1) stem cell-derived CT products or 2)

mature/functionally differentiated cell-

derived CT products. This dichotomous

distinction is important because the final

CT product may contain residual source

cells, and thus may retain some of the

properties of the source cell or tissue from

which it is derived…”

The paragraph describes three types of CT

products. The references to “dichotomy”

of source cells obscure the core issues for

CBT in general and specific concerns

arising from unique attributes of stem cells

are more difficult to discern.

Please edit this section to read:

“CT products can be generally classified as: 1) stem cell-

derived CT products; 2) somatic CT products comprised of

mature/functionally differentiated cell-derived products

which have been manipulated or processed ex vivo or 3)

induced pluripotent stem cell CT products which have the

possibility of expressing characteristics of both stem cell-

derived and somatic cell-derived products. The final CT

product may contain residual source cells, and thus may

retain some of the properties of the source cell or tissue

from which it is derived. The in vivo biological activity and

safety profile of the investigational CT product is strongly

influenced by product origin (donor source, tissue source),

as well as the level of manipulation and stage of

differentiation at the time of administration.”

Page 14-15: A.1-A.2: The concluding sentence of IV.A.2 applies

to both stem cells and somatic cells.

Please add a description of sources of induced pluripotent

cells to the description of tissue sources listed in IV.A.1-2.

We also suggest adding the following sentence:

“Regardless of the type of CT product, if the cells originate

from animal tissue or cells (xenotransplantation products),



additional considerations apply (Refs. 5 and 12).”

Page 15; A.2: “2. Functionally differentiated tissue-

derived CT products may be obtained from

adult human donors (autologous or

allogeneic) or from animal sources

(xenogeneic). Source cells can include

chondrocytes, pancreatic islet cells,

hepatocytes, neuronal cells, and various

immune cells…”

Please edit this paragraph to read:

“2. Somatic Functionally differentiated tissue-derived CT

products may be obtained from adult human donors

(autologous or allogeneic) or from animal sources

(xenogeneic). Source cells can include chondrocytes,

pancreatic islet cells, hepatocytes, neuronal cells, and

various immune cells. CT products derived from functionally

mature tissues typically do not possess the property of self

renewing proliferation and the capacity to differentiate into

multiple cell types; however, they may retain some cellular

characteristics of their tissue of origin. Additionally, their

characteristics may change after in vivo administration,

based on numerous specific extracellular cues. The

characteristics of stem cells and somatic cells may change

after manipulation and in vitro expansion during

manufacture and/or following in vivo administration, based

on numerous specific extracellular cues.”

Please also add a description of sources of induced

pluripotent stem cell therapies (iPSC).

B. ANIMAL SPECIES/MODEL(S)

Page 15-16; B: In some cases animal models of disease

might not be available.

Please clarify if there is a path to the clinic for these types

of diseases.

Page 15; B: “For a general discussion regarding the

selection of biologically relevant animal

species and animal models of

Please replace text with the following:

“Specific considerations for CT products can include:”



disease/injury, refer to Sections III.B.2-3

of this document. Additional considerations

for CT products can include”:

The clarity of this section could be

improved by limiting this section to

specific points applicable to cell based

therapies; more specific guidance with

respect to selection of animal model of

disease and consolidating general

considerations within Section III.B.2-3

rather than repeating and/or expanding

upon them.

Page 15; B: Paragraph 2 is not specific to CT products

but applies generally to CGT products.

We suggest consolidating paragraph 2 with paragraph 3 in

Section III.B. 2-3 on pages 4 and 5 of the Draft Guidance.

Page 15; B: “Administration of human cells into

animals is complicated by the

immunogenic responses of healthy

immune-competent animals, potentially

resulting in the rejection of the

administered human cells. This prevents

adequate evaluation of the activity and

safety of the human cellular product.”

Adequacy of evaluation would not be

limited for cells that would not be

expected to engraft clinically.

Please amend text to read:

Administration of human cells into animals is complicated

by the immunogenic responses of healthy immune-

competent animals, potentially resulting in the rejection of

the administered human cells. Engraftment should be

demonstrated in models for cells that are intended to

engraft. For cells that engraft immunogenic responses can

prevent adequate evaluation of the activity and safety of

the human CT product. This prevents adequate evaluation

of the activity and safety of the human cellular product.



Page 16; B: “The administration of analogous cellular

products in the preclinical studies is also a

potentially acceptable option.12 However,

when preclinical testing is performed using

an analogous cellular product, there will be

uncertainty regarding the relevance of the

data due to potentially different biological

activities, molecular regulatory

mechanisms, and impurities/contaminants.

Therefore, if this preclinical testing

pathway is used, the level of analogy of

the animal cellular product with the

intended human cellular product should be

characterized. Examples of parameters to

evaluate may include:”

The relationship of analogous cells to the

clinical product is best understood by

comparison. In 4. functional properties

need to be relevant to pharmacology of

the clinical product. Pharmacology for

analogous cells should mimic desired

clinical effect. The impact of differences

between analogous cells and the clinical

product need to be considered with

respect to safety and efficacy.

Please amend section to read:

Ideally, the clinical product should be evaluated in

preclinical studies. The administration of analogous cellular

products in the preclinical studies is also a potentially

acceptable option. The scientific value of this approach is

optimized when the analogous CT product is similar to the

CT product. However, when preclinical testing is performed

using an analogous cellular product, there will be

uncertainty regarding the relevance of the data due to

potentially different biological activities, molecular

regulatory mechanisms, and impurities/contaminants.

However, preclinical testing of analogous products

introduces uncertainty regarding the relevance of the data

due to potentially different biological activities, molecular

regulatory mechanisms, and impurities/contaminants.

Therefore, if this preclinical testing pathway is used, the

level of analogy of the animal cellular product with the

intended human cellular product should be characterized by

comparison to the clinical product including the following

parameters. For example: Examples of parameters to

evaluate may include:

1. Established procedures for tissue/sample harvest.

2. Cell identification, isolation, expansion, and in vitro

culture procedures.

3. Cell growth kinetics (e.g., cell doubling time, cell growth

curve, and time to cell proliferation plateau).

4. Phenotype, pharmacology, and functional properties



(e.g., secretion of growth factors and cytokines, cell

population-specific phenotypic/genotypic markers).

5. Final product formulation/cell-scaffold seeding

procedures (as applicable).

6. Final product storage conditions and cell viability.

Ideally, the analogous CT product should be representative

of the preclinical characteristics of the clinical product. For

programs using analogous cells the potential impact of

differences between the analogous cells and the clinical

product on safety and efficacy evaluations as well as human

extrapolation should be assessed.

The degree of similarity of these parameters for the

analogous CT product should be as close to the proposed

human CT product as possible in an attempt to maximize

the applicability of data derived from the animal studies.

C. OVERALL STUDY DESIGN

Page 17; C: We suggest that the core considerations

for study designs and potential safety

concerns be combined, because 1) most of

the listed considerations impact both

safety and efficacy evaluations; and 2)

frequently both safety and efficacy

endpoints for CT products are evaluated in

the same study.

Please combine the core considerations for study designs

and potential safety concerns.



Page 17; C and D: In light of the comment directly above,

please combine and amend these sections

Please combine and amend section(s) to read:

The preclinical program used to support the administration

of a CT product in a specific patient population should be

comprehensive and based on the known biological

attributes of the product. Considerations when designing

preclinical studies for investigational CT products include all

of the following:

1. The source of the cell(s).

2. The cell dose required to achieve a pharmacologically

relevant response.

3. The maximum feasible cell dose or multiple of a

pharmacologically active dose that results in an undesired

response.

4. The fate of the cells post-administration and potential for

migration from the site of administration.

5. The potential impact of a host immune response to the

administered cells on the assessment of safety or efficacy.

6. Potential systemic toxicities, local toxicities and/or

administration site reactions.

7. Potential immune/inflammatory responses in target

and/or non-target tissues.

8. Potential to differentiate into an unintended/

inappropriate cell type (ectopic tissue formation).

9. Unregulated/dysregulated proliferation of the cells within

the host

10. Potential tumorigenicity

11. A rationale for dose extrapolation from animals to

humans

D. SAFETY



Page 17; D:

Please see comments in Section IV.C.

above.

Please combine and amend these sections.

E. CT PRODUCT FATE POST-ADMINISTRATION

Page 18; E: “Determination of the fate of the

investigational CT product following

administration in animals is an important

contribution to characterizing the product

activity and safety profile.”

We believe more specific guidance is

warranted.

Please replace introduction paragraph with the following:

“The objectives of these studies are to determine if cells

engraft and if so, how long they persist as well as to

determine if and where cells migrate from the site of

administration. Pilot studies are encouraged. Generally,

the site of administration as well as highly perfused and

reproductive organs should be evaluated for the presence

of cells. The determination of cell fate does not require

standalone studies but can be accomplished by

incorporation into preclinical safety and efficacy studies.

When conducted early in development, cell fate studies can

help characterize mechanism of action by determining if

engraftment is important for pharmacology; help justify the

choice of relevant animal models and for safety studies

justify study duration and identify potential target organs of

toxicity.”

Page 18; E.1: Text uses the term “survival/engraftment”

but does not define the term which can be

subjectively interpreted many ways.

Please specifically indicate what the Agency considers

evidence of survival/cell engraftment as it relates to the

administered dose.

For example, would the presence of detectable cells at the

lower limit of quantitation of specific assay 1 week post

administration be considered evidence of

survival/engraftment or does it require 1% or 5% of the



administered cell dose to be present for a longer period of

time (e.g., 1 month)? What period of time is considered

long-term survival?

Page 18: E.1: “If long-term cell survival/engraftment is

necessary to achieve effectiveness of the

CT product, effort should be undertaken to

evaluate in vivo cell survival, anatomic

engraftment, and biologic activity over

prolonged periods of time

postadministration.”

Please define:

1. the duration of time the Agency considers “long-term”

cell survival/engraftment and

2. “prolonged periods of time postadministration.”

Page 19: E.3: “Cellular differentiation capacity, the

plasticity of phenotypic expression

attributable to transdifferentiation or

fusion with other cell types, as well as

structural and functional tissue integration,

may all be influenced by physiologic

factors within either the local

microenvironment into which the CT

product is administered or the final

location/niche in which the cells ultimately

reside…”

Most of the text in this paragraph provides no specific

recommendation and repeats information previously

discussed; therefore we recommend it be deleted.

Additionally, we recommend that the last sentence in this

paragraph be rewritten to read:

“Depending on their differentiation status and the extent of

manipulation the cells undergo prior to in vivo

administration, parameters such as cell morphology,

phenotype, and level of differentiation following in vivo

administration should may be assessed in the animal

studies.

Page 19; E.4: “The potential for tumorigenicity,

dysplasia, or hyperplasia to occur should

be considered and addressed as

appropriate for the specific biologic

properties of each investigational CT

product. Factors that may influence the

We suggest this introduction and bullets be rewritten to

read:

“Cells may be tumorigenic. The potential for tumorigenicity,

dysplasia, or hyperplasia to occur should be considered and

addressed based on the CT product attributes. Factors that



tumorigenicity assessment include…”

Specific guidance needs to be provided

with respect to what constitutes an

acceptable tumorigenicity study to prevent

post hoc assessments of validity.

may influence the tumorigenicity assessment include:

a) the differentiation status of cell types within the CT

product;

b) the nature of cell manipulation employed during

manufacture;

c) the expressed transgene (e.g., various growth

factors) for genetically modified CT;

d) the potential to induce or enhance tumor formation

from existing subclinical host malignant cells.”

V. RECOMMENDATIONS FOR INVESTIGATIONAL GENE THERAPY (GT) PRODUCTS

A. INTRODUCTION

Page 22; A: Are non-genetically modified viruses

covered in this scope, such as Newcastle

disease virus which can be used as an

oncolytic virus?

Please clarify if non-genetically modified viruses are

covered in the scope of this guidance.

Page 22; A: Is there a more complete compendium of

products that is available that defines what

is and is not a gene therapy, and as such

covered by this guidance? If so, please

make reference to this.

Please reference the more complete compendium if

available.

B. ANIMAL SPECIES/MODEL(S)

Page 22-23: This section seems overly redundant to It would help in reduction of text to either eliminate section

V.B and make reference to section III.B.2 or eliminate



section III. B 2. section III.B.2 and have the details here.

Page 23; B.3: “Sensitivity of the species to the biological

actions of the ex vivo transduced cells.”

This terminology is different from that

used in point V. A5 on page 22.

Please reconcile terminology within the section:

“Sensitivity of the species to the biological actions of the ex

vivo genetically modified transduced cells.”

Page 23; B: Please clarify Please add a point 5 to read:

“Persistence of vector and/or transgene.”

Page 23; B: “In instances where the expressed

transgene is not biologically active in the

animal species, use of the clinical vector

expressing an analogous transgene that is

active in the laboratory species may

suffice…”

Please harmonize the use of the words “analogous” and

“homologous”. We suggest using either “analog” or

“homolog” when referring to using a surrogate.


Page 23; C: This section seems overly redundant to

section III. B 2.

It would help in reduction of text to either eliminate section

V.B and make reference to section III.B.2 or eliminate

section III.B.2 and have the details here.

D. SAFETY

Page 24; D.1: “Although assessment of the safety of the

in vivo administered vector depends on

the biological properties of each vector

type, common concerns that should be


“Although assessment of the safety of the in vivo

administered vector depends on the biological properties of

each vector type, common concerns that should be



addressed include”

The word “common” should be deleted

from this sentence, since some of these

points to consider are not common.

addressed include”

Page 24; D.1b: “Toxicities due to the ROA (e.g., local vs.

systemic).”

The parenthetical comment here would

suggest that, if a local ROA is used, a

systemic toxicology would also be needed.

This may be the case, depending on

known risks of the agent, however, this

should be on a case by case basis.

Please remove the parenthetical comment so the text

reads:

“Toxicities due to the ROA (e.g., local vs. systemic).”

Page 24; D.1f: “Inappropriate immune activation or

suppression.”

The word “inappropriate” should be

deleted since sometimes this activation is

intended, but still would need to be

monitored as a safety concern.


“Inappropriate Immune activation or suppression.”

Page 24; D.1k: “Potential horizontal transmission of virus

from the patient to family members and

health care providers (i.e., shedding).”

This statement would suggest that there is

a requirement for nonclinical shedding

studies to be performed. In many cases,


“Potential horizontal transmission of virus from the patient

to family members and health care providers (i.e.,

shedding) in the case that a replicating viral vector is

used.”



such studies are not warranted.

Page 26; D.5: This paragraph references “biological

fluids”, does this refer to shedding?

Please clarify what is meant by “biological fluids.”

Page 26-27 D.5: “The characterization of the vector

presence, persistence, and clearance

profile can inform the selection of the GT

product dosing schedule...”

Please clarify if this statement means repeat dosing of gene

therapies.

Page 27; D.5c: “Established vectors with a significant

formulation change.”

Please clarify what constitutes a significant formulation

change.

Page 27; D.5 f and

g:

These two points would appear to include

any gene therapy, since almost every gene

therapy clinical trial utilizes a “new”

transgene, where in the context of gene

therapy, it is unclear what the potential of

toxicity may be.

In addition, there is no data in the public

domain that suggests that a transgene in

a viral vectored gene therapy would affect

biodistribution. The biology of viral

transduction of cells indicates that the viral

protein coat is the determining factor for

how a virus will infect and distribute

throughout an organism. Published data

on viral vectored vaccines bears this

hypothesis out – Sheets, et al. (2008) J

Please delete points f and g.



Immunotoxicol 5(3): 315-35.

Page 27; D.5 last

paragraph:

“In addition, the presence of a vector

sequence in tissues/biological fluids may

trigger further analysis to determine the

transgene expression levels using methods

such as a quantitative Reverse

Transcriptase PCR (RT-PCR) assay.

Quantitation of transgene expression can

help determine 1) the threshold level of

expression associated with beneficial or

deleterious effects for specific

tissues/organ systems and 2) correlation

of the kinetics of transgene expression

with desired activity or undesired toxicity

profiles.”

The need to collect tissues for RNA in

order to better characterize toxicity

assumes a number of things – a) that the

biodistribution study is performed in the

same species as the toxicology study and

b) that an extensive tissue sampling is

taken in the pivotal toxicology study, as it

will be unclear what tissue will experience

toxicity a priori. This would result in a

tremendous amount of work for the

Sponsor that in the vast majority of cases

would be a waste of resources, considering

the general lack of widespread toxicity in

gene therapy preclinical toxicology studies.

The best scientific approach to this issue would be that any

analysis of RNA expression in a particular tissue be linked

with “investigative toxicology” after a toxicological signal is

observed.

Therefore, it is suggested that this section addressing RNA

analysis be deleted from the biodistribution section and the

following statement be made at the end of the introductory

paragraph in section V.D:

“In the event of a toxicological signal, Sponsors may

choose to initiate investigative work to better characterize

the toxicity. This may include sampling tissue in a follow

up study to determine if toxicity was the direct result of

transgene expression.”



Furthermore, such an analysis of RNA

expression is not consistent with the intent

of biodistribution studies, which is simply

to understand how a vector distributes

throughout an organism.

VI. RECOMMENDATIONS FOR INVESTIGATIONAL THERAPEUTIC VACCINES

A. INTRODUCTION

Page 28; A: “Therapeutic vaccines are designed to

elicit host immunological responses

targeted to the destruction or removal of

an antigenic moiety, thereby ameliorating

or treating a specific disease.”

The definition of a “therapeutic vaccine” as

given in the introduction would not cover

anti-allergy vaccines for example, or

vaccination to modulate auto-immune

responses.

Please change the definition of “therapeutic vaccines” to the

following:

“Therapeutic vaccines are designed to elicit or modulate

host immunological responses targeted to the destruction

or removal of an extrinsic or intrinsic antigenic moiety,

thereby ameliorating or treating a specific disease.”


Page 28; C: “In addition, parameters to evaluate

immunological specificity, immune activity,

and the potential for immune toxicity (i.e.

allergy or autoimmune disease) should be

included.”

We are not aware of suitable animal

models to assess the potential for

autoimmune disease.

Please amend the text so it reads:

“In addition, parameters to evaluate immunological

specificity, immune activity, and the potential for immune

toxicity (i.e. allergy or autoimmune disease) should be

included where meaningful preclinical models exist.”

VII. REFERENCES



Page 30; 8 and 9 References 8 and 9 As full characterization of early discovery lots is not feasible

as many analytical methods and criteria are developed in

parallel with later process development, please delete these

two Guidance Document references which imply full release

testing is required.

Documents

Dockets Management Branch (HFA-305) Food and Drug ... BIO...Feb 27, 2013 · drug development preclinical program. We suggest including an introductory paragraph that reads: “The